As discussed in Ref. [1]}, the cross section for the
charm production at large forward rapidities, which is the region of
interest for estimating the prompt \(\nu _{\mu }\)  flux
[2]}, can be expressed as follows
\(d \sigma _{pp \rightarrow charm} = d \sigma _{pp \rightarrow charm}(gg \rightarrow c \bar{c}) + d \sigma _{pp \rightarrow charm}(cg \rightarrow cg) \,\,,\) 
